Optical disc device capable of quick search for a boundary between recorded and unrecorded areas

ABSTRACT

An optical disc recording device in which RF signals reproduced from a write-once optical disc are detected during track jump for detecting the boundary between a recorded area and an unrecorded area on the write-once optical disc. This defines a roughly defined boundary between the recorded and unrecorded areas which may be searched quickly. A more strictly defined boundary between the recorded and unrecorded areas, may be searched quickly by subsequently employing a binary search method to the roughly detected boundary.

FIELD OF THE INVENTION

This invention relates to a write-once optical disc recording device forrecording data on a write-once optical disc by radiating a light beamthereon.

BACKGROUND OF THE INVENTION

In a conventional optical disc device, the information can be recordedby radiating a light beam on a disc-shaped recording medium forsequentially forming pits thereon. Typical of such optical disc deviceis a CD-recordable (CD-R) conforming to the standard for a compact disc.The data structure of a CD-R, may be further appreciated with referenceto the application entitled "Apparatus and Method for Completing andIncomplete Recording on an Optical Disc", U.S. Pat. No. 5,559,778,assigned to the assignee of the present invention and incorporated byreference herein.

The optical disc employed in the CD-R drive device is a write-onceoptical disc in which a light beam of high intensity is radiated thereonfor altering optical properties of the recording layer betweenpre-grooves, which are pre-formed guide grooves, for writing theinformation only once.

On the write-once optical disc, there is provided a program area forrecording data per se, such as speech data. Several methods of datarecording may be used which fall under one of two categories;interrupted writing (or disc at once (DAO)) and uninterrupted writing.The latter category includes track at once (TAO) mode and packetrecording mode (fixed or variable packet). The present invention relatesto interrupted writing.

One method for data recording in the program area is a track-basedwrite-once operation of subsequently writing data track-by-track. In thepresent specification, "track" which should be distinguished from"physical track", means a collection of data corresponding to a file ortwo or more files.

On the write-once optical disc, a lead-in area is formed inwardly of theprogram area, that is towards the disc center. The lead-in area is aregion in which there is recorded management data for management of datarecorded in the program area. Adjacent to the lead-in area towards thecenter of the disc is a program memory area (PMA). The PMA functions asa temporary memory for storing disc identification information as wellas data indicating the portions of the disc that have been used forrecording. Additionally, the PMA stores information concerning the startaddress and the end address of a track. The start and end address of thedata recorded in the PMA area help define a unrecorded area in the PMAso that data may be written to this unrecorded area.

However, there are also occasions wherein data is written once on thebasis of a packet recording, a packet being a unit of data smaller insize than a track. The packet-based data write-once operation is termedthe "in-track write-once" operation. In this case, each track is made upof a variable number of packets and the information concerning the trackstart and end addresses are previously recorded in the PMA area. In the"in-track write-once" operation, data is sequentially recorded insuccession, beginning from the first packet in the track. Afterinterruption of the data recording operation, data recording isre-started at the unrecorded area next to the area in which the lastdata has been recorded.

An important difference between the two aforementioned methods is thatinformation concerning identification of those portions of the PMAhaving data recorded thereon (i.e., the "use state") is recorded in thePMA only on the track basis. The information concerning the "use state"of the program area on the packet basis is not recorded in the PMA.

Consequently, for the "in-track once-write" operation, recorded data isdirectly read out for detecting the unrecorded area, that is fordetermining whether a subject area is a recorded area or an unrecordedarea. To this end, a binary search method is generally employed.However, with the binary search method, the search time becomes longeras the number of physical tracks making up a "track" becomes larger. Asused herein, the "physical tracks" which should be distinguished from"track", means an area scanned by an optical pickup during one completerevolution of the optical disc during data readout.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a write-once optical disc recording device in which theunrecorded area in a file can be searched in a short time.

In accordance with the write-once optical disc device of the presentinvention, RF signals reproduced from the write-once optical disc aredetected during track jump in order to detect a boundary between arecorded area and an unrecorded area on the once-write optical disc. Inthis manner, an approximate boundary between the recorded area and theunrecorded area may be searched quickly.

Once the approximate boundary has been determined, an accurate boundarybetween the recorded area and the unrecorded area may be detected morestrictly using the binary search method. In this manner, a more strictlydefined boundary between the recorded area and the unrecorded area maybe searched quickly.

The boundary between the recorded area and the unrecorded area may bedetected depending on the number of physical tracks of the area to besearched on the write-once optical disc using 1) both the method ofdetecting RF signals reproduced from the once-write optical disc duringtrack jump and using the middle point search method or 2) only thebinary search method. In this manner, the boundary between the recordedarea and the unrecorded area may be searched quickly, while the timesince insertion of the optical disc into the disc writing device untilstart of the data once-write operation may be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an arrangement of awrite-once optical disc recording device according to the presentinvention.

FIG. 2 is a flow chart for illustrating the sequence of retrieving theboundary between a recorded area and a unrecorded area.

FIG. 3 is a flow chart for illustrating the sequence of retrieval usingRF signals during track jump.

FIG. 4 is a flow chart showing the sequence of search operations using abinary search method according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail. FIG. 1 shows, in schematic blockdiagram, a schematic arrangement of a write-once optical disc recordingdevice according to the present invention.

During data recording data such as speech data transmitted from anexternal host computer enter a signal input terminal 43 via aninterfacing circuit. The data is transmitted to an encoder 28 where itis encoded an convened into recording signals. These recording signalsare equalized by a timing generating circuit 48 and thence transmittedto a laser modulating circuit 29. The data writing timing signals fromthe timing generating circuit 48 are transmitted to a matrix circuit 11.The laser modulating circuit 29 converts the equalized recording signalsinto a laser light output power which is transmitted to a laser diode 1.

The laser light (light beam) radiated from the laser diode 1 based onthe laser output light power is collimated by a collimation lens 2 so asto be guided via a grating 3 and a beamsplitter 4 to an objective lens 6whereby it is converged on a write-once optical disc 7. In this manner,the light beam illuminated on the optical disc 7 is controlled inintensity depending on "1" or "0" of the data for recording desired dataon the disc.

Part of the light beam incident on the beam splitter 4 is separated bythe beam splitter 4 so as to be incident on a laser monitor 5 where itis convened into a signal indicating its power. The signal istransmitted to a monitor head amplifier 30 and thereby amplified beforebeing transmitted to an automatic power control (APC) circuit 31. Usingthe signal from the monitor head amplifier 30, the APC circuit 31controls the power of the light beam outgoing from the laser diode 1 soas to be constant without regard to extraneous factors, such astemperature. The control signal from the APC circuit 31 is transmittedto a laser modulating circuit 29. Using the control signal from the APCcircuit 31, the laser modulating circuit 29 controls the power of thelight beam radiated from the laser diode 1 so as to be constant.

The reflected light of the light beam radiated on the optical disc 7 isincident on the beam splitter 4 via the objective lens 6. The beamsplitter 4 guides the incident light from the disc to a multiple lens 8.The multiple lens is made up of a cylindrical lens and a converging lensand converges the incident light on a photodetector 9.

An output of the photodetector 9 is amplified by a head amplifier 10 soas to be outputted to a matrix circuit 11. The matrix circuit adds orsubtracts outputs of the head amplifier 10 for generating a trackingerror signal TE, a focusing error signal FE and a push-pull signal PP.

The tracking error signal TR and the focusing error signal FE arerespectively transmitted to phase compensation circuits 12 and 13. Thephase compensation circuit 12 phase-compensates the tracking errorsignal TE for servo control. The phase-compensated signals aretransmitted to a driving circuit 14. The driving circuit 14 actuates atracking actuator 16, using signal from the phase compensation circuit12, for correctly shifting the objective lens 6 to a mechanical neutralposition which is the pre-set tracking position in the radial directionof the optical disc 7. In the phase compensation circuit 13, thefocusing error signals FE are phase-compensated for servo control. Theresulting phase-compensated signals are transmitted to a driving circuit15. The drive circuit 15 actuates a focusing actuator 17, using a signalfrom the phase compensation circuit 13, for vertically shitting theobjective lens 6 relative to the optical disc 7 for converging the lightbeam more correctly on the recording surface of the optical disc 7.

The low-frequency component of the tracking error signal TE is fed to athread phase compensation circuit 32 for phase compensation. Thephase-compensated signals are transmitted to a driving circuit 33. Thedriving circuit 33 drives a thread motor 34 using the phase-compensatedsignals from the thread phase compensation circuit 32 for shifting theposition of a thread mechanism 44 in a controlled manner. This causescontrolled movement of an optical pickup, made up of the elements 1 to10, along the radial direction of the optical disc 7.

The matrix circuit 11 outputs the push-pull signal PP which is fed to awobbling detection circuit 21. The wobbling detecting circuit 21 detectswobbling which is outputted to an ATIP demodulator 22. The ATIPdemodulator 22 detects ATIP and ATIP readout clock signals from thedetected wobbling. The detected ATIP and ATIP readout clock signals arefed to an ATIP decoder 23. The ATIP decoder 23 reproduces the addressinformation with the aid of the ATIP and ATIP readout clock signals. Thereproduced address information is fed to a CPU 24.

The wobbling detected by the wobbling detection circuit 21 and the ATIPreadout clock signals detected by the ATIP demodulator 22 are alsooutputted to a spindle servo circuit 25. The spindle servo circuit runsa spindle motor 27 in rotation via a motor driver 26 using the wobblingand the ATIP readout clock signals supplied thereto. At this time, thespindle servo circuit 25 controls the frequency of the wobbling detectedby the wobbling detection circuit 21 to be constant at 22.05 kHz orcontrols the frequency of the ATIP readout clock signals outputted bythe ATIP modulator 22 to be constant at 6.35 kHz.

Before proceeding to data write-once operation, the above-describedwrite-once optical disc recording device searches for the boundarybetween the recorded area and the non-recorded area.

FIG. 2 shows, in a flow chart, the sequence of operations of searchingfor the boundary between the recorded area and the unrecorded areaaccording to one aspect of the present invention.

At step S1, the values of the leading address and the trailing addressof a "track" to be searched are stored, as values of the leading addressand the trailing address of an area to be searched, in a memory, notshown, enclosed in the CPU 24. At step S2, it is judged whether or notthe size of the area under retrieval is not more than a preselectednumber of "physical tracks"; e.g., 3000. If the size of the area to besearched is not more than this preselected number, the position of aboundary between the recorded area and the unrecorded area is detectedby using only the binary search method of step S4 (as explained furtherwith reference to FIG. 4.), skipping step S3. If the size of the area tobe searched is more than the preselected number of physical tracks, stepS3 is carded out where a rough boundary search is carded out using theRF signals reproduced during track jump in order to detect the roughposition of the boundary between the recorded area and the unrecordedarea. An accurate boundary search is then performed using the binarysearch method of step S4 for accurately detecting the boundary betweenthe recorded area and the unrecorded area.

FIG. 3 shows, in a flow chart, the search sequence employing RF signalsreproduced during track jump according to another aspect of the presentinvention.

At step S11, the optical pickup is set to the leading end of the area tobe searched on the optical disc 7 by the seek operation. Control thenshifts to step S12 in order to effect track jump towards the lastaddress of the area to be searched.

In effecting such track jump, the laser light is radiated from the laserdiode 1 (FIG. 1) onto the optical disc 7 at a playback power. The lightradiated to and reflected back from the optical disc 7 is received bythe photodetector 9, which then outputs a signal indicating the receivedlight volume to the matrix circuit 11 via the head amplifier 10. Thematrix circuit 11 generates the tracking error signal TE and thefocusing error signal FE. These error signals are used for movementcontrol of the tracking actuator 16 and the focusing actuator 17. Thematrix circuit 11 also outputs RF signals, as reproduced signals, whichare transmitted to an RF detection circuit 45. The RF detection circuit45 judges whether or not data components are contained in thetransmitted RF signals. The results of judgement are transmitted to theCPU 24.

The CPU 24 judges at step S13 whether or not the trailing end of thearea to be searched or the unrecorded area in the area to be searchedhas been reached. If as yet the trailing end of the area to be searchedor the unrecorded area within the area to be searched is not reached,track jump is again made and the judgement step of S13 is repeated. Ifit is judged at step S13 that the trailing end of the area to besearched or the unrecorded area in the area to be searched has beenreached, the tracking servo and the thread servo are turned on at stepS14 in order to make a halt at a position slightly advanced from thedetected position.

Subsequently, it is judged at step S15 whether or not the currentposition of the optical pickup is more inward than the trailing end ofthe area to be searched. If the current position is found in this manneras being more inward than the trailing end of the area to be searched,the address value of the current position is set at step S16 to be theaddress value of the trailing end of the area to be searched. Thisnarrows the area to be searched. If the current position is found as notbeing more inward than the trailing end of the area to be searched, theobjective lens position surpasses the trailing end of the area to besearched. Consequently, the objective lens position is set to thetrailing end of the area to be searched at step S17 by the seekoperation.

Then, at step S18, track jump is made towards the leading end of thearea to be searched, and it is then judged at step S19 whether or notthe leading end of the area to be searched or the recorded area in thearea to be searched has been reached. If it is found that the leadingend of the area under retrieval or the unrecorded area in the area to besearched has not been reached, track jump is made towards the leadingend of the area to be searched in order to repeat the judgement step ofstep S19. However, if it is found that the leading end of the area to besearched or the recorded area in the area to be searched has beenreached, the tracking servo and the thread servo are turned on at stepS20 in order to make a halt at a position further slightly advanced fromthe detected position.

At step S21, it is judged whether or not the current position of theoptical pickup is more outward than the leading end of the area to besearched. If it is found in this manner that the current position of theoptical pickup is more outward than the leading end of the area to besearched, control shifts to step S22 where the current address value isset as being the address value of the leading end of the area to besearched. The sequence of retrieval is now terminated. The above processnarrows the area to be searched. If it is found at step S21 that thecurrent position of the optical pickup is not more outward than theleading end of the area to be searched, the sequence of retrieval isterminated, with the address value of the leading end of the area to besearched remaining unchanged.

By performing the track jump and judging whether or not data has beenrecorded from the reproduced RF signals, the approximate boundarybetween the recorded area and the unrecorded area may be searchedquickly.

FIG. 4 shows, in a flow chart, the sequence of search operations by thebinary search method according to the present invention.

At step S31, it is judged whether or not the area to be searched, as setby employing the RF signals during the previous track jump, has beendiminished to not more than a preselected number of "physical tracks",e.g., 4. If it is determined that the area to be searched is not lessthan this preselected number of physical tracks, control shifts to stepS32 in order to start a seek operation towards the center of the area tobe searched; that is towards the trailing end.

During the seek operation, the RF signals as detected by the matrixcircuit 11 are routed to a bi-level circuit 18 where the signal areturned into corresponding bi-level signals. The resulting signals arerouted to a PLL circuit 19, where clock signals are reproduced from thehi-level signals and are routed along with the bi-level signals to adecoder circuit 20. The decoding circuit 20 decodes the bi-level signalswith the aid of the clock signals. This reproduces the data and thesub-code. The reproduced data is outputted at an output terminal 42,while the sub-code is transmitted to the CPU 24. The CPU 24 performsdata control using the transmitted sub-code.

The clock signals reproduced by the PLL circuit 19 are fed to thespindle servo circuit 25 as readout clocks of the RF signals so as to becompared to reference clock signals. The resulting comparison output isrouted to the motor driver 26 as a rotation error signal produced at thetime of data reproduction. The motor driver 26 controls the rotationaldriving of the spindle motor 27 with the aid of the rotation errorsignal.

It is then judged at step S33 whether or not the current position of theoptical pickup is recorded. If the current position is recorded, controlshifts to step S34 where the address value of the current position isstored in the memory as being the address value of the leading end ofthe area to be searched. If the current position is not recorded,control shifts to step S35 where the address value of the currentposition is stored in the memory as being the address value of thetrailing end of the area to be searched. If the operation of the stepsS34 or S35 comes to a close, control reverts to step S31 where it isdetermined whether or not the size of the area to be searched is notmore than the preselected number of physical tracks. The above sequenceof operations is repeated until the size of the area to be searched isnot more than the preselected number of physical tracks.

If it is found at step S31 that the size of the area to be searched isnot more than the preselected number of physical tracks, control shiftsto step S36 for performing a seek operation to the leading end of thearea to be searched. Subsequently, at step S37, it is judged whether ornot the current optical pickup position is recorded. If it is found inthis manner that the current position is not recorded, the currentposition represents the boundary between the recorded area and theunrecorded area. Thus the address value of the current position isstored at step S39 in the memory to terminate the boundary search by thebinary search method.

On the other hand, if it is found at step S37 that the current positionhas been recorded, control shifts to step S38 where it is determinedwhether or not the trailing end of the area to be searched has beenreached. If it is found that the trailing end of the area to be searchedhas been reached, the address value of the current position is stored inthe memory at step $39 to terminate the boundary search by the binarysearch method. If there is no unrecorded area in the area to besearched, the trailing end position of the area to be searched may bedetected in the manner described above.

If it is found at step S38 that the trailing end position of the area tobe searched has not yet been reached, the seek operation is furtherperformed towards the leading end of the area to be searched in order torepeat the operation of judging whether or not the current position atstep S37 is recorded.

It is noted that the size of the area to be searched, which isdetermined before starting the boundary search, and the size of the areato be searched, which is initially determined for the binary searchmethod, may be set to optional values other than those given in theabove embodiments.

What is claimed is:
 1. An optical disc recording device in which a lightbeam is radiated on an optical disc for recording data thereon, saidoptical disc having recorded and unrecorded areas, said optical discrecording device comprising:a tracking actuator; a circuit foroutputting error signals to control movement of said tracking actuatorand for outputting RF signals during track jump of said trackingactuator; rough boundary detecting means for receiving said RF signalsand for roughly detecting a boundary between said recorded andunrecorded areas; and fine boundary detecting means for finely detectingsaid boundary by a binary search method.
 2. The optical disc recordingdevice according to claim 1, wherein said boundary between said recordedand unrecorded areas is roughly detected by said rough boundarydetecting means and then finely detected by said fine boundary detectingmeans when the number of physical tracks in a search area of saidoptical disc is greater than a predetermined number and wherein saidboundary is finely detected by said fine boundary detecting meanswithout rough detection by said rough boundary detecting means when saidnumber of said physical tracks in said search area of said optical discis not greater than said predetermined number.
 3. The optical discrecording device as claimed in claim 1, wherein said optical disc is awrite-once optical disc.
 4. An optical disc device for reading andrecording data from and onto an optical disc including a number ofphysical tracks for storing said data thereon, said optical disc devicecomprising:optical pickup means for reproducing signals by radiating alight beam onto said optical disc; a tracking actuator for conveyingsaid optical pickup means in a radial direction of said optical disc; RFsignal detection means for detecting whether RF signals are included insaid signals reproduced by said optical pickup means; a memory forstoring addresses of a leading end and a trailing end of a search areaof said optical disc, said search area having a recorded region and anunrecorded region therein; and control means for controlling saidoptical pickup means, said tracking actuator and said RF signaldetection means to search a boundary between said recorded region andsaid unrecorded region within said search area, wherein said controlmeans searches said boundary via a binary search method where the numberof said physical tracks in said search area is less than a preselectednumber and wherein said control means searches said boundary viadetecting said RF signals and then via said binary search method wherethe number of said physical tracks in said search area is not less thansaid preselected number.
 5. An optical disc recording device in which alight beam is radiated on an optical disc for recording data thereon,said optical disc having recorded and unrecorded areas, said opticaldisc recording device comprising:a tracking actuator; a circuit foroutputting error signals to control movement of said tracking actuatorand for outputting RF signals during track jump of said trackingactuator; rough boundary detecting means for receiving said RF signalsand for roughly detecting a boundary between said recorded andunrecorded areas; and fine boundary detecting means for finely detectingsaid boundary by a dichotomizing search method.
 6. The optical discrecording device according to claim 5, wherein said boundary betweensaid recorded and unrecorded areas is roughly detected by said roughboundary detecting means and then finely detected by said fine boundarydetecting means when the number of physical tracks in a search area ofsaid optical disc is greater than a predetermined number and whereinsaid boundary is finely detected by said fine boundary detecting meanswithout rough detection by said rough boundary detecting means when saidnumber of said physical tracks in said search area of said optical discis not greater than said predetermined number.